The present invention relates to substituted nicotinamide compounds, to a process for their preparation, to medicaments comprising these compounds and to the use of these compounds in the preparation of medicaments.
The treatment of pain, in particular of neuropathic pain, is of great importance in medicine. There is a worldwide need for effective pain therapies. The urgent need for action for a target-orientated treatment of chronic and non-chronic states of pain appropriate for the patient, by which is to be understood successful and satisfactory pain treatment for the patient, is also documented in the large number of scientific works which have recently been published in the field of applied analgesics and of fundamental research into nociception.
A pathophysiological feature of chronic pain is the overexcitability of neurons. Neuronal excitability is influenced decisively by the activity of K+ channels, since these determine decisively the resting membrane potential of the cell and therefore the excitability threshold. Heteromeric K+ channels of the molecular subtype KCNQ2/3 (Kv7.2/7.3) are expressed in neurons of various regions of the central (hippocampus, amygdala) and peripheral (dorsal root ganglia) nervous system and regulate the excitability thereof. Activation of KCNQ2/3 K+ channels leads to a hyperpolarization of the cell membrane and, accompanying this, to a decrease in the electrical excitability of these neurons. KCNQ2/3-expressing neurons of the dorsal root ganglia are involved in the transmission of nociceptive stimuli from the periphery into the spinal marrow (Passmore et al., J. Neurosci. 2003; 23(18): 7227-36). It has accordingly been possible to detect an analgesic activity in preclinical neuropathy and inflammatory pain models for the KCNQ2/3 agonist retigabine (Blackburn-Munro and Jensen, Eur J Pharmacol. 2003; 460(2-3); 109-16; post et al., Naunyn Schmiedebergs Arch Pharmacol 2004; 369(4): 382-390). The KCNQ2/3 K+ channel thus represents a suitable starting point for the treatment of pain; in particular of pain selected from the group consisting of chronic pain, neuropathic pain, inflammatory pain and muscular pain (Nielsen et al., Eur J Pharmacol. 2004; 487(1-3): 93-103), in particular of neuropathic and inflammatory pain.
Moreover, the KCNQ2/3 K+ channel is a suitable target for therapy of a large number of further diseases, such as, for example, migraine (US2002/0128277), cognitive diseases (Gribkoff, Expert Opin Ther Targets 2003; 7(6): 737-748), anxiety states (Korsgaard et al., J Pharmacol Exp Ther. 2005, 14(1): 282-92), epilepsy (Wickenden et al., Expert Opin Ther Pat 2004; 14(4): 457-469) and urinary incontinence (Streng et al., J Urol 2004; 172: 2054-2058).